When the Air Hits Your Brain: Tales from Neurosurgery

by Frank T. Vertosick Jr.

Even though the bleeding during an SAH can be slight and doesn’t damage the brain substance directly, it is a devastating event. A person may silently harbor an aneurysm for years until some stress, such as sexual intercourse, lifting a heavy box, or simply having a violent sneeze, sends a pulse wave of blood pressure that splits the fragile aneurysm sac, spilling a torrent of arterial blood into the space between the brain and the skull. This region is called the “subarachnoid space” because it is below the arachnoid, a cottony substance which covers the brain and which derives its name from its close resemblance to a spider’s web. The victim of an SAH is felled immediately by a “thunderclap” headache, as if shot by a gun. Vomiting may occur. The body reacts quickly to stem the hemorrhage by sending the blood vessels feeding the aneurysm into spasm, temporarily closing them off. Arterial spasm is the body’s natural defense against hemorrhage—it’s what allows a Kansas farmboy the time to pick up his arm after it has been amputated by a threshing machine and run for help without bleeding to death. An arm can go hours without blood and survive. The brain’s survival time without oxygen is three minutes. Several minutes after a brain aneurysm ruptures, the feeding arteries are compelled to reopen by chemical signals from the starving brain tissue. If a sufficient protective clot has not formed over the rent in the aneurysm’s wall, the bleeding will resume, with lethal results....

Oh good, this helps me sleep at night.